Fuel cell power plant having a fuel concentration sensor cell

Abstract

A fuel cell power plant ( 10 ) having a fuel concentration sensor cell ( 54 ) is disclosed for detecting a concentration of fuel in a fuel cell ( 12 ) of the plant ( 10 ). A portion of a fuel exhaust stream is directed to flow through the sensor cell ( 54 ) adjacent to a membrane electrode assembly ( 60 ) of the sensor cell ( 54 ). A power circuit ( 62 ) may or may not deliver an electrical current to the cell ( 12 ), while changes in voltage across the cell ( 12 ) that are proportional to changes in hydrogen concentrations within the fuel exhaust stream are detected by a detector ( 68 ) which communicates the changes to a controller ( 108 ) for controlling a rate of fuel supply to the fuel cell ( 12 ). A porous sensor water transport plate ( 74 ) cools, humidifies delivers and removes liquid from the sensor cell ( 12 ).

1. A fuel cell power plant ( 10 ) for generating electrical current, the plant comprising:
 a. at least one fuel cell ( 12 ) having a fuel inlet ( 28 ) and a fuel exhaust ( 50 ) for directing flow of a hydrogen containing reducing fluid fuel into and out of the fuel cell ( 12 ); 
 b. a fuel concentration sensor cell ( 54 ) for detecting concentration of the reducing fluid fuel in the fuel cell ( 12 ), the sensor cell ( 54 ) including;
 i. an anode flow field ( 56 ) and a cathode flow field ( 58 ) disposed on opposed sides of a membrane electrode assembly ( 60 ); 
 ii. a power circuit ( 62 ) for selectively delivering electrical current through the membrane electrode assembly ( 60 ); 
 iii. a detector ( 68 ) secured in electrical communication with the membrane electrode assembly ( 60 ) for detecting an electrical signal between opposed sides of the membrane electrode assembly ( 60 ); and, 
 iv. wherein the sensor cell ( 54 ) is secured in fluid communication with the fuel exhaust ( 50 ) so that a portion of a fuel exhaust stream passes through the sensor cell ( 54 ); 
 
 c. a porous sensor water transport plate ( 74 ) secured in fluid communication with the sensor cell ( 54 ) for directing a cooling fluid to pass adjacent the sensor cell ( 54 ) to remove heat and condensate water from the sensor cell ( 54 ) to maintain humidity of the membrane electrode assembly ( 60 ); and, 
 d. a controller means ( 108 ) for controlling operation of the fuel cell ( 12 ) secured in electrical communication with the detector ( 68 ) and in communication with a fuel inlet valve means for controlling a rate of supply of the reducing fluid fuel to the fuel cell ( 12 ) in response to communication from the detector ( 68 ). 
 
   
   
     2. The fuel cell power plant ( 10 ) of  claim 1 , wherein a sensor fuel feed line ( 52 ) directs the portion of the fuel exhaust stream to flow only through the anode flow field ( 56 ) of the sensor cell ( 54 ), and a power supply switch ( 66 ) of the power circuit ( 62 ) is closed to direct an electrical current through the membrane electrode assembly ( 60 ). 
   
   
     3. The fuel cell power plant ( 10 ) of  claim 1 , wherein a sensor fuel feed line ( 52 ) directs the portion of the fuel exhaust stream to flow through one side of the sensor cell ( 54 ), a second sensor feed line ( 130 ) directs a portion of a fuel inlet stream to flow through an opposed side of the sensor cell ( 54 ), and a power supply switch ( 66 ) of the power circuit ( 62 ) is closed to direct an electrical current through the membrane electrode assembly ( 60 ). 
   
   
     4. The fuel cell power plant ( 10 ) of  claim 1 , wherein, the membrane electrode assembly ( 60 ) of the sensor cell ( 54 ) includes catalysts without any carbon support materials secured to at least one side of the membrane electrode assembly ( 60 ). 
   
   
     5. The fuel cell power plant ( 10 ) of  claim 1 , wherein, the membrane electrode assembly ( 60 ) of the sensor cell ( 54 ) includes a palladium black catalyst secured to at least one side of the membrane electrode assembly ( 60 ). 
   
   
     6. The fuel cell power plant ( 10 ) of  claim 1 , wherein the porous sensor water transport plate ( 74 ) is secured in fluid communication with a sensor coolant pressure control means ( 92 ) for maintaining a positive pressure differential between any fluid streams passing trough the sensor cell ( 54 ) and the cooling fluid passing through the sensor water transport plate ( 74 ). 
   
   
     7. The fuel cell power plant ( 10 ) of  claim 1 , wherein the fuel inlet valve means includes a hydrocarbon fuel processing reformer fuel inlet valve ( 36 ), a reformer oxidant inlet valve ( 42 ), a hydrogen fuel inlet valve ( 48 ), a fuel recycle blower ( 72 ) secured to a fuel recycle line ( 70 ), or combinations thereof, all of which are secured in fluid communication with the fuel inlet. 
   
   
     8. A fuel cell power plant ( 10 ) for generating electrical current, the plant comprising;
 a. at least one fuel cell ( 12 ) having a fuel inlet ( 28 ) and a fuel exhaust ( 50 ) for directing flow of a hydrogen containing reducing fluid fuel into and out of the fuel cell ( 12 ); 
 b. a fuel concentration sensor cell ( 54 ) for detecting a concentration of the reducing fluid fuel in the fuel cell ( 12 ), the sensor cell ( 54 ) including;
 i. an anode flow field ( 56 ) and a cathode flow field ( 58 ) disposed on opposed sides of a membrane electrode assembly ( 60 ); 
 ii. a detector ( 68 ) secured in electrical communication with the membrane electrode assembly ( 60 ) for detecting an electrical signal between opposed sides of the membrane electrode assembly ( 60 ); and, 
 iii. wherein the sensor cell ( 54 ) is secured in fluid communication with the fuel exhaust ( 50 ) so that a portion of a fuel exhaust stream passes through the sensor cell ( 54 ); 
 
 c. a porous sensor water transport plate ( 74 ) secured in fluid communication with the sensor cell ( 54 ) for directing a cooling fluid to pass adjacent the sensor cell ( 54 ) to remove heat and condensate water from the sensor cell ( 54 ) and to maintain humidity of the membrane electrode assembly ( 60 ); and, 
 d. a controller means ( 108 ) for controlling operation of the fuel cell ( 12 ) secured in electrical communication with the detector ( 68 ) and in communication with a fuel inlet valve means for controlling a rate of supply of the reducing fluid fuel to the fuel cell ( 12 ) in response to communication from the detector ( 68 ). 
 
   
   
     9. The fuel cell power plant ( 10 ) of  claim 8 , wherein a sensor fuel feed line ( 52 ) directs the portion of the fuel exhaust stream to flow only through one side of the sensor cell ( 54 ), and an oxidant supplied to the fuel cell ( 12 ) is directed to flow through an opposed side of the fuel cell ( 12 ). 
   
   
     10. The fuel cell power plant ( 10 ) of  claim 8 , wherein a sensor fuel feed line ( 52 ) directs the portion of the fuel exhaust stream to flow to one side of the sensor cell ( 54 ), and a second sensor feed line ( 130 ) directs a portion of a fuel inlet stream to flow through an opposed side of the sensor cell ( 54 ). 
   
   
     11. The fuel cell power plant ( 10 ) of  claim 8 , wherein, the membrane electrode assembly ( 60 ) of the sensor cell ( 54 ) includes catalysts without any carbon support materials secured to at least one side of the membrane electrode assembly ( 60 ). 
   
   
     12. The fuel cell power plant ( 10 ) of  claim 8 , wherein, the membrane electrode assembly ( 60 ) of the sensor cell ( 54 ) includes a palladium black catalyst secured to at least one side of the membrane electrode assembly ( 60 ).